This invention relates generally to liquid transfer devices, and more particularly to improvements in tip ejectors for hand-held micropipettors.
Within the last few years, hand-held micropipettors have become very popular as laboratory instruments, primarily in medical laboratories. The following United States patents describe existing instruments supplied by Oxford Laboratories Inc., the assignee of the present application: RE 27,637 -- Roach (1973); 3,855,867 -- Roach (1974); 3,882,729 -- Roach (1975); and 3,918,308 -- Reed (1975). Such devices include a tube-like barrel body structure having a plunger assembly extending outward of one end thereof terminating in a liquid transfer operating knob. A piston is attached to the other end of the plunger within a piston chamber. The piston chamber is maintained in fluid communication with an aperture at an end of the barrel handle which is shaped for frictionally engaging a detachable tip. The piston is held in a normal rest position by one or more springs within the barrel handle. When used to transfer liquid, the pipettor plunger is depressed, the attached tip is placed in a liquid and the plunger released to draw liquid into the tip. The pipettor is then removed to a container for discharge of the liquid. The liquid is discharged from the tip by again depressing the plunger.
After discharge, it is often desirable to remove the used plastic tip from the end of the micropipettor and dispose of it. A fresh tip is utilized for subsequent pipetting of different liquids in order to prevent cross-contamination. Rather than requiring the operator to force the tip off the micropipettor by manual pulling, some devices provide detipping mechanisms which are used by the operator to force a used tip off the micropipettor without having to touch the used pipette tip. Micropipettors with detipping devices are shown in the aforementioned U.S. Pat. No. 3,918,308 and also in additional U.S. Pat. Nos. 3,853,012 -- Scordato (1974) and 3,766,785 -- Smernoff (1973). Each of these patents describe a micropipettor that requires a separate hand operation to remove pipette tips therefrom that is in addition to the hand operations required to transfer liquid with the device. It is a principal object of the present invention to provide a tip ejecting structure for a hand-held micropipettor that is operable as part of the same hand manipulation which occurs during liquid transfer.